Limax gerhardti
| Limax gerhardti | ||||||||||||
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| Limax gerhardti | ||||||||||||
| Riveting hammer , 1937 |
Limax gerhardti is a species of nudibranch from the family of snails (Limacidae), which belongs to the land snails (Stylommatophora).
features
Limax gerhardti is stretched out to about 15 cm long (13 cm). It is uniformly deep black with fine longitudinal wrinkles. The sole is divided into three sections lengthways. The middle field is pink, the two side fields are colored dark pink with a narrow black border. The keel is short. The front edge of the mantle shield is rounded, the rear edge slightly angled.
The hermaphroditic gland sits in the apical part of the viscera and is approximately wedge-shaped. It consists of several lobes. The thin hermaphroditic corridor is strongly twisted and partly spiraled. The egg duct (spermoviduct) is comparatively short and surrounded by a large prostate gland. The free fallopian tube remains approximately the same thickness, with no terminal enlargement. The seminal vesicle is small and pear-shaped with a short stem. When copulating, the penis is 22 to 50 mm long (average 35 to 38 mm). When turned up, the apical part is slightly constricted. The spermatic duct (vas deferens) opens almost at the tip into the constricted part of the penis; The penile retractor muscle starts directly at the tip. The spermatic duct wraps around the penis several times.
Similar species
Limax gerhardti (so far) differs from all other Limax species in its complex copulation behavior. Due to the three-part sole with red-colored side panels and the sexual biology, it belongs to the Corsicus group s. l. The restriction "so far" refers to the fact that the copulation behavior of only a few species has been examined in detail.
Geographical distribution and way of life
The species is endemic to the Italian island of Ischia . Nothing is known about the way of life outdoors. In captivity, the animals were fed cucumbers, carrots and lettuce.
Reproduction
The copulatory behavior of this species was described in great detail by Ulrich Gerhardt. This begins with the pursuit of an animal ready to mate for hours by another animal ready to mate. The pursuer always puts the tail tip of the pursued. The chase ends some height above the ground, either on the underside of a branch or on a vertical surface. The animals now form a circle in which the pursued animal bends over to the right behind. It takes about an hour to crawl around in a circle. At the end the circle becomes narrower and tighter and finally the animals place their heads on the partner's coat on the right. Then they knock their heads together like a hook, biting and forming slime. The bodies detach themselves further and further from the base with further wrapping. The grip is very tight at first, then loosens again to tighten again. This is repeated several times. At the tip of the tail, both partners each form a triangular slime sail with which the animals are attached to the base during the actual copulation. Finally the violent movements stop and the heads hang down at the same height. Only then do the penes emerge from the genital orifices, initially only briefly and about 2 mm thick. Gradually they continue to lengthen. The tips curve into the horizontal and the two penes begin to look for each other. Once contact has taken place, they wrap themselves in a spiral and slowly turn out to their full length (22 to 50 mm long, ø 35 to 38 mm). This phase can last 2 hours or more. As soon as the penis reaches an everted penis length of 10 cm, the sperm packets appear at the base of the penes. They are brownish-yellow, wheat-grain-sized bodies, which are also referred to as spermatophores in the literature. More and more blue fluid (hemolymph) collects in the spiraled penis. This is now pumped higher than the sperm packages by rhythmically shortening and lengthening the penes and also through constant rotating movements, in order to then generate pressure above the sperm packages by pressing the penis bases. This continuous pumping process and the subsequent build-up of pressure gradually move the sperm packets to the tips of the penis. The blue liquid and the sperm packets do not initially reach the spiraled end part of the penis. The last phase of the migration of the sperm packets is initiated by shortening the penis to about 3/4 of the length it has already reached. Then blue fluid will also appear below the sperm packets and above the spiraled end portions of the penes. The penes become longer again and with violent turns and peristaltic movements of the penes, the sperm packets are now pressed through the spiraled parts and remain about 5 mm in front of the penis tip. The migration of the sperm packets from appearing to reaching the penis tips often takes two hours or more. The penes now reach their full length. With the exception of a short spiraled part above the tips, they hang parallel and close to one another. Although the combs extend over the entire length, they are only weakly developed and therefore hardly appear. Only at the tips are they shovel-shaped. The free tips below the spiraled penis part are curved almost horizontally and carry out gripping movements. The blue liquid has now collected in the tips, the sperm packets stand out clearly in color. In the spiraled part, the blue liquid is constantly pumped up and down. The penes are now shortened, the extensions no longer reach their full length. When a penis length of 8 to 10 cm has been reached, the sperm packets are transferred. The sperm package first slides onto the shovel-shaped combs, these grip the partner's penis and stick the sperm package on the outside of the penis. Only a little later, the same process takes place on the part of the other partner. The transfer only takes seconds. While with other Limax species the separation of the intertwined penes and body is initiated, the intertwined penes of L. gerhardti or the strongly broadened combs form a hat-shaped structure that is very clearly set off against the thin bases of the penis. This stage can take up to 1½ hours. Only then do the combs retract and the glued-on sperm packages become visible. The penes are then shortened further by pulling them in, briefly everting them, which no longer reaches their original length, and pulling them in again. The sperm packets are placed inside the tips of the penes. When it is drawn in, the secreted mucus, including any foreign bodies that may be attached, is stripped off the penes and finally falls to the floor. This last phase lasts up to two to five hours, in exceptional cases up to eight hours. Only when the penes have completely disappeared into the genital orifices (atria) does the head appear under the coat and the antennae are stretched out. One animal then climbs up on the body of the other animal, over the slime sail to a solid base, then the second animal too. Both animals are now crawling away from each other, no further contact takes place. Copulation can take place several times in a season. In total, copulation from the formation of a circle to separation takes about five to six hours, in exceptional cases up to 11 hours.
It has not yet been investigated whether self-fertilization is possible without a partner. In one case, U. Gerhardt observed a couple in copula in which the transfer of the sperm packets failed because the crests of the penis did not unfold in one of the partners. As a result, the sperm package could not be transferred to the partner's penis, and the transfer of the other partner's sperm package did not take place either, so that the two animals each withdrew their own sperm packages. It has not been investigated whether fertilization with their own sperm occurred.
The copulation period lasted from August to October in captivity. Observations from the field are not available.
Taxonomy
The taxon was basically already recognized by Ulrich Gerhardt in 1937 and partly also described (as Limax sp.). This was followed by the work of Günther Niethammer , who scientifically formally described the taxon and named it after Ulrich Gerhardt. The species has almost been forgotten and has only recently been noticed again.
supporting documents
literature
- Gerhardt, Ulrich 1937. Further studies on the sexual biology of the Limacids. Journal for Morphology and Ecology of Animals, 32 (3): 519-541, Berlin (pp. 525-535). doi : 10.1007 / BF00406839
- Niethammer, Günther 1937: Limax gerhardti n. Sp., A new nudibranch species from Italy. Meeting reports of the Society of Friends of Natural Sciences in Berlin, 1936: 443–444, Berlin.
- Gerhardt, Ulrich 1944: Sexual Biology and Morphology, illustrated by two examples. 44 p., Niemeyer, Halle (Saale).
Individual evidence
- ^ Niethammer (1937): p. 443/4
- ↑ a b Falkner, Gerhard & Margrit Falkner 2006: Present-day knowledge of the copulation modi within the genus Limax . MalaCo, 3: 105 PDF ( Memento of the original dated November 13, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
